The next thing you know, hapless Joe Biden’s next warning to threats from Iran will change from “Don’t” to “Please don’t.”

What a difference an election makes!

When Donald Trump was president and Iranian President Hassan Rouhani warned in 2018 that the U.S. would suffer the “mother of all wars” in a conflict with the Iranian state, Trump responded in all caps:

“NEVER THREATEN THE UNITED STATES AGAIN, OR YOU WILL SUFFER THE CONSEQUENCES THE LIKES OF WHICH FEW THROUGHOUT HISTORY HAVE EVER SUFFERED BEFORE.”

Biden says, “Don’t.”

And when top Iranian Quds Force Gen. Qassem Soleimani, responsible for the death of hundreds of American troops in Iraq, was planning another attack on U.S. interests, Trump had him blown up outside the Baghdad airport in 2020.

Trump said, “We took action last night to stop a war. We did not take action to start a war.”

Not only did the “Death to America” crowd go silent in Tehran, but Trump’s strict economic sanctions on Iran caused it to go broke.

Those sanctions, unenforced by Biden, meant billions of dollars in oil income to the mullahs. It was money they used to finance their terrorist proxies and their military.

Biden would have said “Don’t” to the killing of Soleimani just as he did as vice president when he advised President Barack Obama not to assassinate Osama bin Laden, the architect of 9/11, during a raid on his hideout in Pakistan in 2011.

Biden, in the White House Situation Room, said he told Obama, “Mr. President, my suggestion is don’t go.”

Obama ignored Biden, just as leaders around the world ignore Biden now, no matter how many times “Don’t Go, Joe” says “Don’t, don’t, don’t, don’t, don’t.”

This includes Russian dictator Vladimir Putin with his invasion of Ukraine, Iranian Supreme Leader Ayatollah Ali Khamenei, with his attacks on Israel, and Israeli Prime Minister Benjamin Netanyahu with his offensive against Hamas.

Hardly had Biden warned Iran with his foreign policy doctrine based on the word “Don’t,” than Khamenei fired 300 drones and missiles into Israel, practically all of which were shot down by Israeli forces, along with substantial help from the US, the UK and Jordan.

Biden attempted to paint the failed attack as a win for Israel, just as he called his precipitous and botched withdrawal from Afghanistan a success.

Only the Israelis are not buying it, nor should they, even though the damage was minimal and showed how inept the Iranians are at missile warfare.

Biden, seeking to avoid a regional war which some say has already begun again said “Don’t” to the Israelis who planned to retaliate with an attack on Iran.

And the Israelis ignored him again with their attack on Iran Friday, just as they are ignoring his demands for a cease-fire in Gaza before the Israelis complete their wipeout of all the Hamas terrorists.

If Biden were president during the successful U.S.-led June 6, 1944, Normandy invasion he probably would have called for a cease-fire at the end of The Longest Day to give the Germans time to recuperate.

Meanwhile, Biden sounds like Nancy Regan during her White House years when the wife of President Ronald Reagan launched her “Just Say No” campaign against drug use.

That went over so well that today, some 100,000 Americans a year are now dying from Chinese-induced fentanyl, and marijuana is being legalized everywhere.

The fact is that, unlike attacks from Iranian-backed proxies like Hamas, Hezbollah, and the Houthis, the latest attack, incompetent as it was, was launched from Iranian soil, which was a game changer.

So, Israel responded in kind, despite Biden’s most recent “Don’t” warning.

As Mike Pompeo, Trump’s secretary of state said, “Don’t is not a national security policy.”

But it does not matter. Nobody takes Biden seriously anyway. Not a joke.

Peter Lucas is a veteran political reporter. Email him at: peter.lucas@bostonherald.com

A woman walks past a banner showing missiles being launched, in northern Tehran, Iran, Friday. Iran fired air defenses at a major air base and a nuclear site near the central city of Isfahan after spotting drones early Friday morning, raising fears of a possible Israeli strike in retaliation for Tehran’s unprecedented drone-and-missile assault on the country. On the missiles, a decorative sign reads: “Allah” (AP Photo/Vahid Salemi)